1. Field of the Invention
This invention relates generally to the field of particle decontamination during manufacturing of semiconductor devices, a plurality of which are formed on a wafer, and particularly to a method and apparatus for reducing particle contamination of the wafer while the wafer is in a vacuum, in-situ.
2. Description of the Prior Art
Semiconductor devices are manufactured on a smaller scale due to a variety of recent applications of semiconductor, microelectronic and microelectro-mechanical devices requiring small-scale devices. Small scale device manufacturing further increases the need for wafer decontamination.
During semiconductor device manufacturing, wafers are typically formed in vacuum deposition tools, such as vacuum plasma processing tools, with the wafer being loaded outside of the vacuum and then brought into the vacuum for thin film deposition and various ion etching or other processing. However, the functionality of devices produced by such procedures can be severely impaired if foreign substances, in the form of micro particulate, are contaminating the surface of the wafer. Such contamination usually comes from poor handling and outdated tool design and inadequate manufacturing controls.
In applications, such as magnetic disk recording drives, utilizing microelectromagnetic devices, the presence of undesirable particles on the wafer surface thereof is similarly detrimental in that, for example, if a particle is in line with a critical dimension of a device feature in the recording head (a device used to read and/or write to the magnetic recording disk), the disk drive is essentially rendered inoperational. That is, the head devices on the contaminated wafer are essentially wasted.
For a better understanding, an extreme case is shown here on the wafer particle contamination. FIG. 1 shows a graph 10 of prior art problems, such as particle signal multiplication occurrence due to malfunctions of tool-resident mechanical components. This graph depicts the impact of an unintended internal particle source. All prior art methods, since they are ex-situ standing-alone non-integrated methodologies, are “upstream” and ineffective. Particle contamination, as shown by the y-axis 12, is shown against chronology, as shown by the x-axis 14, for a wafer being 5 inches in diameter. Multiplication of particle contamination introduces particles into the critical dimension of heads of disk drives essentially reduces yield and raises manufacturing unit costs.
Prior art technology has attempted to reduce wafer contamination. For example, electrostatic decontamination devices are utilized but no method or apparatus offers decontamination to take place directly within the vacuum tool or in-situ. The prior art electrostatic decontamination devices typically have two gas flow openings, one is referred to as inlet and the other is referred to as outlet. Flow of gas, which is needed for decontamination, requires pressure differential. With help of electrostatic charge, particles are “lifted” and “vacuumed” into a particle collector by the presence of gas flow. However, this technique, firstly, requires a separate device, i.e. the electrostatic decontamination device and secondly gas flow is required to blow particles. The disadvantage of such ex-situ particle reduction devices is that the method is useless for contamination from an internal source such as a malfunctioning vacuum deposition tool (e.g. during wafer mechanical transferring between process modules). That is, it is vacuum incompatible. The state-of-the-art recording head processing technology, and microelectronic processing, in general, calls for multi-layer and multi-module processing cluster equipment with integrated complex mechanical systems, which increase exposure to in-situ contamination due to increased frequency of wafer in situ mechanical handling. Such limitation of prior art ex-situ particle decontamination devices is therefore inadequate in reducing such contamination related yield and reliability problems. The only viable solution to such problem is increased tooling, renewal and increase in maintenance frequency resulting in increased productivity costs and cycle time. The challenge is then to reduce or ideally eliminate particle contamination while in-situ in vacuum, and perhaps utilizing existing vacuum tools without modification thereto.
In summary, in prior art techniques, a particle ionizing device is employed for decontamination of the surface of the wafer, however, this is a stand-alone device specifically designed for particle contamination and requiring added steps for this purpose, and is only good for decontamination of upstream ex-situ sources.
Thus, in light of the foregoing, there is a need for a wafer decontamination method and apparatus compatible with vacuum processing requirement and integrated into microelectronic thin film processing tools.